A variety of polysiloxane-polyether or polysiloxane polyoxyalkylene copolymers are known in the art, and the copolymers have found many uses including the manufacture of polyurethane foams and emulsification of one of a pair of immiscible liquids in the other, such as water-in-oil, oil-in-water and oil-in-oil emulsions.
The use of polysiloxane surface active agents comprising organic polyether groups to stabilize emulsions is well known. U.S. Pat. No. 4,421,656 disclose terpolymeric polydiorganosiloxanes as stabilizers for solids-free invert emulsions for the deep well-drilling art. U.S. Pat. No. 4,254,878 uses a polysiloxane surface active agent to stabilize antiperspirant stick compositions. U.S. Pat. No. 4,218,250 uses such a polysiloxane surface active agent to stabilize polish formulations. U.S. Pat. No. 4,268,499 uses such surface active agents to stabilize antiperspirant emulsion compositions. Further, U.S. Pat. No. 4,311,695 uses such surface active agents in personal care creams and the like.
Special mention is made of U.S. Pat. No. 5,008,103, which discloses polysiloxane containing organic polyether groups. However, the polysiloxanes of the present invention have improved stability when employed with mineral oils, cyclic methylsiloxane fluids and the like in water-in-oil emulsions.
Polysiloxane surface active agents are sometimes referred to as polysiloxane-polyoxyalkylene copolymers. However, their use to date as stabilizers for silicone emulsions, particularly water-in-oil emulsions, has not always been completely satisfactory because the variables affecting their function are not well understood. Water-in-oil emulsions which contain high concentrations of salts or other ionic materials are often particularly difficult to stabilize. The problems encountered in formulating emulsions of antiperspirants in volatile fluids are exemplary of this.
Antiperspirant compositions are well known in the cosmetic art. These compositions are formulated as aerosols, gels, sticks, creams, pump sprays and lotions and comprise an astringent, typically comprising one or more zirconium salts and/or aluminum salts, in various forms such as dry, impalpable powder, an alcohol solution or an aqueous solution. Of these various forms of astringents, the aqueous solution is generally considered to be the most effective antiperspirant.
An antiperspirant composition having water as the continuous phase, such as an aqueous solution of an astringent, or an oil-in-water type emulsion thereof, is less desirable because it tends to feel wet when applied to the human skin and to go through a tacky state during the drying period after application. Therefore the use of water-in-oil emulsions to apply antiperspirants to the skin has found favor.
U.S. Pat. No. 4,122,029 discloses water-in-oil type compositions having broad utility and comprising a polydiorganosiloxane-polyoxyalkylene copolymer and a water-in-oil type surfactant. When formulated as an antiperspirant emulsion of an aqueous solution of an astringent such as aluminum chlorohydrate emulsified in a volatile, non-aqueous continuous phase, these compositions have a desirable dry feeling when applied to the human skin.
U.S. Pat. No. 4,268,499 discloses compositions described as having greater efficacy than those of U.S. Pat. No. 4,122,029. The efficacy was determined by applying compositions to subjects' wrists and measuring the time required for the composition to dry and turn white.
Another type of water-in-oil emulsion which has found favor with the public is polishes, particularly for furniture. One drawback to furniture polishes which utilize organic or organosilicone surfactants comprising long chain oxyalkylene residues, particularly long chain oxyethylene residues, is that the surfactant may tend to attack the finish of the article to be polished. This is particularly the case when the finish is based on nitrocellulose lacquers, since glycol ethers are solvents of choice for nitrocellulose finishes.
There has now been found a novel family of silicone polyether/alkyl copolymers which exhibit significant improvements in forming a wide variety of water-in-oil emulsions for use in products such as antiperspirants, hair shampoos or conditioners, hand creams, lotions, tanning oils and polishes (auto and furniture). Surprisingly, water-in-oil emulsions employing the silicone polyether copolymer emulsifiers of the present invention, exhibit significantly improved stability over prior art emulsions when emulsified with mineral oils, cyclic methyl siloxanes and other oily phase emollients.